In recent years, various kinds of security products for preventing a main body of a personal computer (hereinafter referred to as “PC”) from being stolen and for protecting data preserved in a PC have been on the market. As for such security products, for example, there are known:                an authentication key for controlling log-in and log-out of a PC by being inserted in and removed from a universal serial bus (USB) port,        a data encryption key for carrying out encryption and decryption in accordance with insertion and removal of the data encryption key in and out the USB port, and        a PC card for detecting shocks and vibrations accompanying a movement of a PC with an acceleration sensor to judge whether or not the PC is stolen.        
In mobile communication terminals such as a mobile telephone and mobile electronic apparatuses such as a personal digital assistant (PDA), during log-in and an access to important data, whether or not a user is a legitimate user is authenticated using a password (personal identification number). Those electronic apparatuses preserve therein important data such as personal information of a user similarly to the case of the PC. Thus, it is necessary to take measures against burglary of a main body of an electronic apparatus and shoulder hack of data.
From this viewpoint, a conventional mobile telephone has a function called a dial lock (keylock) for making a key input electronically invalid. However, recognition of the dial lock function (keylock function) to users is low. In addition, a series of manipulations for setting a dial lock state and for releasing a setting state in restarting use of the mobile telephone using this function are troublesome for a user. Thus, the number of users who usually utilize such a dial lock function is not so many. Moreover, the apparatus configuration for requiring a user to input a password (personal identification number) when the user accesses important data is troublesome for a legitimate user.
Then, in recent years, a folding mobile telephone including a mechanical lock mechanism and a fingerprint authentication unit has come onto the market. In this folding mobile telephone, when chassis are folded, the lock is automatically engaged in a state where the chassis are folded, and the chassis can not be returned back to an open state unless the lock state is released. Therefore, the folding mobile telephone can be prevented from being unlawfully used.
Now, in the mobile telephone for which the mobile property is regarded as important, since a battery (rechargeable battery) which is installed for the operation is also miniature, there is a limit to a power supply capacity. Thus, in general, the mobile telephone is required to reduce the power consumption during the operation as much as possible. Consequently, in the mobile telephone having the lock mechanism as described above, the supply of an electric power is desirably stopped for each functional portion which is inhibited from being used in the lock state.
However, the supply of the electric power to the fingerprint authentication unit used to release the lock state can not be stopped (turn-OFF of a power supply) even in the lock state because the fingerprint authentication for a legitimate user must be speedily carried out. On the other hand, in the case of the apparatus configuration adapted to stop the supply of the electric power to the fingerprint authentication unit in order to reduce the power consumption, there is required a mechanism for restarting the supply of the electric power (turn-ON of the power supply) to the fingerprint authentication unit by some means or other.
Then, JP2002-368870A proposes an apparatus configuration adapted to carry out fingerprint authentication when a user manipulates an authentication start key in order to release such a lock state.
However, in a case where an exclusive manipulation key for switching an operation state of a fingerprint authentication unit is provided in a mobile telephone, the construction of the mobile telephone becomes complicated. Also, in this case, the labor of a user for releasing the lock state is increased. In particular, the apparatus configuration adapted to force a user to carry out a plurality of manipulations under the situation where an incoming call sound of a mobile telephone is ringing is not preferable.